Now I see what you are talking about, there are some real placement pros on here so they will figure that out easily..
If it were me...
I would set it up normally, heres what I figure when you are watching tv you will be sitting in front of it...
I would put the 2 towers in the front on the left and right of the entertainment-center, a sub behind them on the sides of the center, the center in the middle {in cabinet above tv with the face a little closer to you than the tv}, the first surround on the wall a couple feet over the seating area and the other surround on a stand to the left of the couch facing the other surround... It will sound good... Ive seen worse that worked...
For $800 run and buy them sale items, that big room will sound just fine...
The surrounds are rear ported so I would test a few things, plug them, or use an Omni mount on the wall mounted oneto give it a little room, Im sure it will be fine... This isnt a critical listening room, you want a decent theater, you will have a pretty impressive setup..